Cholera is a potentially life threatening disease endemic to many parts of the world. The disease manifests as an acute, diarrheal illness that, if untreated, can lead to severe dehydration and kidney failure. Cholera is caused by infection of the small intestine with the bacterium Vibrio cholerae (V. cholerae), usually via the oral-fecal route. Due in part to its extremely short incubation period (two hours to five days), devastating cholera outbreaks can arise very quickly.
Though cholera is often preventable and treatable, it is still responsible for many deaths due to lack of access to adequate medical facilities. The World Health Organization recommends that cholera vaccines be used in endemic areas. Existing cholera vaccines are too expensive and require complex logistics for distribution. Many countries where cholera is endemic, such as Bangladesh, cannot afford even the cheapest of the currently existing cholera vaccines. Due to instability of current vaccine formulations, a temperature-controlled system for distribution such as a cold chain is required. Such a requirement increases the cost of cholera vaccines. Thus, cholera vaccines often do not reach those who would benefit from such protection. Affordable, stable cholera vaccines that can be distributed more widely to cholera-endemic areas would be advantageous.
Outer membrane vesicles (OMVs) are shed from Gram-negative bacteria including V. cholerae. These vesicles are spherically shaped and average between 50 and 250 nm in diameter. They are comprised of a lipid bilayer containing integral or surface associated outer membrane (OM) proteins, phospholipids as well as lipopolysaccharide. and also enclose bacterial proteins that were present in the periplasmic space.